It wont be automatically upgraded:
https://learn.microsoft.com/en-us/azure/information-protection/configure-policy-migrate-labels
The license requirements are the same:
https://learn.microsoft.com/en-us/office365/servicedescriptions/microsoft-365-service-descriptions/microsoft-365-tenantlevel-services-licensing-guidance/microsoft-365-security-compliance-licensing-guidance#which-licenses-provide-the-rights-for-a-user-to-benefit-from-the-service